From 89693ad01d4375e04d6f28603269aa60f409bac1 Mon Sep 17 00:00:00 2001
From: Ally Bowles <abowles@hireology.com>
Date: Mon, 14 Oct 2019 18:17:44 -0500
Subject: [PATCH] Calculate heat index

---
 .bin/wx | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/.bin/wx b/.bin/wx
index 17defb8..01752ad 100755
--- a/.bin/wx
+++ b/.bin/wx
@@ -10,6 +10,7 @@
 # http://www.met.tamu.edu/class/metar/quick-metar.html
 # http://www.dixwx.com/wxdecoding.htm
 # https://en.wikipedia.org/wiki/Wind_chill#North_American_and_United_Kingdom_wind_chill_index
+# https://en.wikipedia.org/wiki/Heat_index#Formula
 
 ## Dependencies:
 # bc
@@ -236,9 +237,13 @@ _temperature_conversion() {
     esac
 }
 
+_calculate_humidity() {
+    humidity=$(bc -l <<< "100 * (e((17.625 * $dp)/(243.04 + $dp))/e((17.625 * $temp)/(243.04 + $temp)))")
+}
+
 humidity() {
     _temperature_dewpoint
-    humidity=$(bc -l <<< "100 * (e((17.625 * $dp)/(243.04 + $dp))/e((17.625 * $temp)/(243.04 + $temp)))")
+    _calculate_humidity
     printf "%.0f%%" $humidity
 }
 
@@ -256,4 +261,20 @@ wind_chill() {
     _temperature_conversion $wind_chill $1
 }
 
+heat_index() {
+    _temperature_dewpoint
+    _calculate_humidity
+    c1="-8.78469475556"
+    c2="1.61139411"
+    c3="2.33854883889"
+    c4="-0.14611605"
+    c5="-0.012308094"
+    c6="-0.0164248277778"
+    c7="0.002211732"
+    c8="0.00072546"
+    c9="-0.000003582"
+    heat_index=$(bc <<< "$c1 + $c2 * $temp + $c3 * $humidity + $c4 * $temp * $humidity + $c5 * $temp ^ 2 + $c6 * $humidity ^ 2 + $c7 * ($temp ^ 2) * $humidity + $c8 * $temp * ($humidity ^ 2) + $c9 * ($temp ^ 2) * ($humidity ^ 2)")
+    _temperature_conversion $heat_index $1
+}
+
 $@ && _check_last_modified || refresh